There are many examples in the prior art of multi-purpose kitchen appliances which are designed for performing such functions as mixing, blending, juicing, food chopping and the like. None of these prior art multi-purpose appliances have been particularly successful from a commercial standpoint. The reasons for this lack of commercial success relates to the compromises or inadequacies associated with these prior art appliances.
For a multi-purpose appliance to be practical and to appeal to the housewife, it must be arranged so that it may be used to perform any one of its selected functions without substantial conversion or rearrangement of the parts and must perform these functions substantially as effectively as the appliances available for performing these functions separately. The basic problem involved in simply using a common power unit to drive a food mixer, a blender and a food grinder or chopper relates to the differences in power and drive speeds required for these various appliances. The food mixer, for example, must supply a substantial amount of power at variable power speeds from a few hundred RPM to about a thousand RPM. The blender, on the other hand, must be driven at speeds far in excess for those suitable for food mixing, i.e. on the order of as high as 17,000 RPM and finally, a food grinder must supply substantially greater power at very low speeds, i.e. on the order of 150 RPM. None of the prior art appliances have provided a suitable means of coping with these various speed and power requirements.
The patent to Strauss et al U.S. Pat. No. 2,278,187 is an example of a combination mixer and blender wherein the power unit comprises a motor which is disposed with its shaft extending vertically and with a turntable for a mixer bowl disposed on a base extending laterally from the base for the power unit. A head is provided which secures to the top of the power unit and supports beater elements which extend into the mixer bowl. In addition, the power unit is provided with means for supporting a blender vessel connected directly to the motor shaft. In addition, a food grinder is provided which connects to the power supporting head to permit the chopping and grinding of meat and food. The power supporting head in the above-cited Strauss et al patent requires a substantial speed reduction between the output shaft of the power unit and the beater spindles. In addition, there is a further substantial reduction going from the drive for the beater spindles to the drive for the meat chopper. The result was a complex arrangement which included a large number of expensive gears and inefficient worm gearing and resulted in an arrangement which compromised the various power requirements and did not have the attachments arranged for easy use. One of the most significant problems involved in an arrangement such as is disclosed by the Strauss et al patent is providing adequate cooling of the reduction gearing. Since the meat grinder particularly requires a substantial amount of power, there is much heat generated in the gearing with little opportunity for fan cooling of the gears as would be possible if located in the area of the motor.
Other multi-purpose appliances are disclosed in Frank U.S. Pat. No. 2,795,958 which shows a combination mixer, blender and chopper; in Schottle U.S. Pat. No. 2,801,545; Moore U.S. Pat. No. 2,685,435 and Vaughn U.S. Pat. No. 2,807,447 which show a combination blender and mixer; and in Sprague U.S. Pat. No. 2,917,929 and Corbett et al U.S. Pat. No. 2,798,700 which show power units for use with various types of appliances. The patent to Sprague is of interest in teaching the broad idea of providing a power unit having two output shafts which are concentric to each other with one providing a relatively high speed output and the other providing a relatively low speed output. Another prior art patent of interest directed to a combination mixer and blender is Australian Pat. No. 151,296 which shows the blender adapted to be driven from a shaft extending from one end of the mixer housing.